Localized triplet excitations and the effect of photo-oxidation in ladder-type poly<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo>(</mml:mo><mml:mi>p</mml:mi></mml:math>-phenylene) and oligo<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mo>(</mml:mo><mml:mi>p</mml:mi></mml:math>-phenylene)

List, Emil; Partee, J.; Shinar, J.; Scherf, Ullrich; Müllen, Kläus; Zojer, Egbert; Petritsch, K.; Leising, G.; Graupner, W.

doi:10.1103/physrevb.61.10807

Cited by 62 publications

(55 citation statements)

References 42 publications

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“…For m-LPPP, TSC measurements have revealed mostly shallow traps with a density of at least 2ϫ10 16 cm Ϫ3 for polarons with an average activation energy of 60 meV, 26 in agreement with the energetic disorder parameter ϭ50 meV ͑Ref. 37͒ found from time-of-flight measurements.…”

Section: Bimolecular Decaysupporting

confidence: 63%

“…This difference in ⌬H 1/2 is attributed to the decreased polaron pair separation ͑and hence increasing dipolar broadening͒ in the oligomer, in agreement with results found from a comparison of these resonances in frozen m-LPPP solutions and m-LPPP films. 25,26 There it was found that ⌬H 1/2 is drastically reduced in solution due to the increased chain separation. In the polymer and oligomer of this work the situation is similar due to the much smaller side groups of the latter.…”

Section: Methodsmentioning

confidence: 99%

“…The dissociation, i.e., the creation yield of polarons, is enhanced by an external electric field, 7 by chemical defects, 26 and by energetic disorder of the material. In addition, n p also depends on the polaron lifetime p .…”

Section: B Polaron Dynamics In Pamentioning

confidence: 99%

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Interaction of singlet excitons with polarons in wide band-gap organic semiconductors: A quantitative study

et al. 2001

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The steady-state photoinduced absorption ͑PA͒, photoluminescence ͑PL͒, PL-detected magnetic resonance ͑PLDMR͒, and PA-detected magnetic resonance ͑PADMR͒ of poly-and oligo-͑para-phenylenes͒ films is described. In particular, the excitation density ͑laser power͒ N 0 dependence of the PA, PL, and PLDMR signals is analyzed by means of a rate equation model, which describes the dynamics of singlet excitons ͑SE's͒ and polarons in all three experiments quantitatively with the same set of parameters. The model is based on the observations that mobile SE's are quenched by trapped and free polarons and that the spin-1 2 magnetic resonance conditions reduce the total polaron population. Since the sublinear N 0 dependences of the positive ͑PL-enhancing͒ spin-1 2 PLDMR and the polaron PA band are essentially the same, we conclude that PLDMR is due to a reduced quenching of SE's by polarons. The agreement between the model, the current results, and results from other spectroscopic techniques provides strong evidence for this quenching mechanism. This also suggests that it is a very significant process in luminescent -conjugated materials and organic light-emitting devices. Consequently, the quenching mechanism needs to be taken into account, especially at high excitation densities, which is of great importance for the development of electrically pumped polymer laser diode structures.

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Section: Bimolecular Decaysupporting

confidence: 63%

Section: Methodsmentioning

confidence: 99%

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Interaction of singlet excitons with polarons in wide band-gap organic semiconductors: A quantitative study

et al. 2001

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“…If it is assumed that the polymer chain is divided into segments bound by conformational or chemical defects, one normally assumes that the singlet exciton occupies most of the segment, a phenomenon known as the effective conjugation length ͑typically 25-30 repeat units͒. 41,42 Conversely, the triplet exciton is understood to only occupy a segment of a few phenyl rings; [43][44][45] thus, if the reasonable assumption that each chain segment can only hold one excitation ͑either singlet or triplet͒, then the mean distance from the singlet to the neighboring triplet exciton is large and the necessary overlap of the states required for intrachain STA by Dexter transfer would not be possible. Additionally, given this constraint, the singlet would be outside the Förster radius of the triplet and the energy transfer could not proceed by a Forster mechanism either.…”

Section: Singlet-triplet Annihilationmentioning

confidence: 99%

Exciton annihilation in a polyfluorene: Low threshold for singlet-singlet annihilation and the absence of singlet-triplet annihilation

et al. 2007

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(2007) 'Exciton annihilation in a polyuorene : low threshold for singlet-singlet annihilation and the absence of singlet-triplet annihilation. ', Physical review B., 76 (8) Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Ultrafast photoinduced absorption measurements have been used to directly investigate singlet-singlet annihilation in polyfluorene. The pump fluence threshold for annihilation to dominate the decay was measured to be ϳ1 J cm −2 corresponding to an excitation density of 1.5ϫ 10 17 cm −3 . The annihilation rate was found to be faster than that expected from a simple dipole-dipole interaction. This is ascribed to the additional influence of diffusion which, because of the dispersive nature of the exciton migration, has strong time dependence as the singlet excitons thermalize in the density of states as well as the expected intrinsic time dependence from a diffusion controlled process. Also, a comparable background level of triplets was created in the film to study the effect of singlet-triplet annihilation, which surprisingly, given the low threshold for singlet-singlet annihilation, was found to be negligible.

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“…The availability of soluble PPV oligomers makes it possible to study their intrinsic molecular properties, and extrapolate to the behaviour of the related polymer [5,7,13,14]. Moreover, the study of these compounds in dilute solutions allows their characterization in the absence of significant effects due to interchain interactions and under conditions where the time between collisions of two oligomers is longer than the lifetimes of the excited states under investigation.…”

Section: Introductionmentioning

confidence: 99%

Electronic spectral and photophysical properties of some p-phenylenevinylene oligomers in solution and thin films

Melo

Pina

Paolo³

et al. 2006

Chemical Physics

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A comprehensive photophysical and spectroscopic study of a new class of p-phenylenevinylene oligomers (PPV-trimers) possessing different alkyl and alkyloxy sidechain substituents and different end groups (aldehyde, C@C, phenylene and anthracene units) was undertaken in solution at room temperature (293 K), low temperature (77 K) and in thin films. The study comprises absorption, emission and triplet-triplet absorption spectra, together with quantitative measurements of quantum yields (fluorescence, intersystem crossing, internal conversion and singlet oxygen formation) and lifetimes. The data allow the determination of rate constants for all decay processes. From these, several conclusions could be drawn. Changing from alkyl to alkyloxy substituents does not change fluorescence and internal conversion yields but decreases the (already small) intersystem crossing yield. The introduction of anthracene at the terminal ends of the PPV-trimers leads to the lowest fluorescence yield reported in this study. Of particular importance is the fact that the fluorescence quantum yields in films are of the same order of magnitude as those in solution, which suggests the potential for use of these oligomers for light-emitting device applications. With one of the alkyloxy derivatives, a more detailed study of the early part of the fluorescence decay was made, and it was found that upon excitation a fast conformational relaxation process of the initially excited oligomer occurs, leading to a more planar conjugation segment.

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Localized triplet excitations and the effect of photo-oxidation in ladder-type poly(p-phenylene) and oligo(p-phenylene)

Cited by 62 publications

References 42 publications

Interaction of singlet excitons with polarons in wide band-gap organic semiconductors: A quantitative study

Interaction of singlet excitons with polarons in wide band-gap organic semiconductors: A quantitative study

Exciton annihilation in a polyfluorene: Low threshold for singlet-singlet annihilation and the absence of singlet-triplet annihilation

Electronic spectral and photophysical properties of some p-phenylenevinylene oligomers in solution and thin films

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